The present invention relates to a technology for controlling an engine torque during DPF (Diesel Particulate Filter) regeneration for heavy construction equipments.
In general, a diesel engine converts the thermal energy into the mechanical energy using the mixed gas of an external air and a diesel fuel as the working fluid, in which the mixed gas is combusted explosively and exhausted out. The combusted mixed gas is exhausted through the exhaust pipe. The exhaust gas includes carbon dioxide, carbon monoxide, hydrocarbon, sulfur oxide, sulfur hydrogen, nitrogen oxide, ammonia, ozone, oxidant, etc. which cause environmental contamination if exhausted into the air as it is without treatment. Recently, the exhaustion of the noxious gases has been remarkably decreased due to the advanced technology of the exhausted gas reduction system.
However, the environmental criterion on the exhaustion of noxious gas of the vehicles is getting more reinforced to resolve the environmental problems of global warming and air pollution. In particular, the exhaustion criterion on the noxious gas exhausted from the heavy construction equipment is getting tightened.
In case of the heavy construction equipment such as excavator, DPF with DOC (Diesel Oxidation Catalyst) inside is connected to the exhaust pipe, oxidizes carbon monoxide, hydrocarbon, etc., and collects PM (Particulate Matter) to meet the exhaustion criterion.
In order to prevent the soot particles collected in the muffler of diesel engine from being accumulated in the filter and clogging the filter, the soot particles are burnt out at regular intervals so that DPF can be regenerated by the reuse of filter. If the soot particles are excessively accumulated in the filter, it not only deteriorates the engine performance but damages the filter during the DPF operation. In the worst case, it may turn off the engine.
In such DPF regeneration, the fuel is additionally injected to increase the exhausted gas temperature to the temperature required for DPF regeneration to burn Out the soot particles collected into carbon dioxide.
In the conventional method applied for excavator DPF regeneration, the engine rpm is increased to a certain level to raise the temperature high enough for the regeneration. However, the plastic load which, is generated by the friction torque occurring when the equipment is not in use and is different depending on the equipment case by case may bring about the change in engine rpm, which leads to the different result of the regeneration of the equipment case by case. This takes place as opposed to the case of using the engine test rig in which a certain level of rpm is maintained by calibrating optimally for the regeneration.
If an optimal engine rpm is not achieved in DPF regeneration, the DPF regeneration may be cancelled and there is possibility that the exhaust fumes or soot is not completely removed due to the temperature oscillation in the DOC (Diesel Oxidation Catalyst). As a result, the DPF regeneration may be frequently required and thus affect the operation time of the equipment.
Accordingly, it is desirable to provide a solution to maintain an optimized torque value for the regeneration by matching with the torque indicated in an engine regeneration calibration that is obtained by increasing a plastic load of heavy construction equipments.
In accordance with an aspect of the present invention, the flow rate of main pump or gear pump is increased if the plastic load of heavy construction equipments with an optimized calibration for DPF regeneration is low and the resulting engine torque is lower than an engine torque required for the DPF regeneration. Accordingly, the engine torque is adjusted to a target engine torque indicated for optimal DPF regeneration. Thus, the optimal DPF regeneration as in the test rig can be achieved in heavy construction equipments.
According to an aspect of the present invention having the above-described scheme, an exhaust gas temperature can be increased to a temperature high enough for DPF regeneration by increasing an engine torque to a target value using main pump or gear pump. If the exhaust gas temperature is not high enough, the DPF regeneration is stopped and the equipment should repeatedly try to regenerate DPF. According to an aspect of the present invention, the shortening of regeneration cycle due to the DPF regeneration failure can be avoided and the unnecessary fuel usage can be saved increasing the running time of the equipment. At the same time, the exhaust gas and soot can be completely removed by optimizing the DPF performance.